I don't believe you for your 999 out of 1000 repos, but I'm not sure how we'd check that. When I browse people's GitHub profiles it's almost all little forks of things they're clearly using in their work.
I don't know what people think OSS is - it's not hobbies. The majority of our infrastructure is OSS - operating systems, compilers, browsers, virtual machines, tools, it's almost all OSS and all majority paid contributors.